Storm Prediction Center Highlights NCEP Production Suite Review December 2, 2014 Steven Weiss, Israel Jirak, Chris Melick, Andy Dean, Patrick Marsh, and Russ Schneider Storm Prediction Center, Norman, OK National Weather Center Outline • Good news and thanks from SPC • SPC mission and responsibility • Convection-allowing model (CAM) forecasts for some high-impact 2014 severe weather cases – Focus on NAM Nest and HiResW upgrades and HRRR implementation • CAM ensemble systems – How do we move forward operationally as experimental CAM ensembles continue to proliferate? Thanks From SPC Perspective • Continued very reliable, timely operational model production • Forums for enhanced collaboration are paying dividends • Weekly EMC Model Evaluation Group (MEG) webinars • Bi-Weekly/Monthly EMC-SPC telecons/webinars focusing on convectionallowing model improvements (NAM Nest, HiResWindow) • Bi-Weekly GSD-SPC telecons/webinars focusing on RAP and HRRR development • Improvements in Convection-Allowing Models for severe weather forecasting support • NAM Nest, HiResW NMMB and ARW upgrades • Operational HRRR implementation • Closer integration of model development efforts with severe weather forecasting needs have been occurring – need to maintain momentum • Consistent with NOAA/NWS strategic goals of Weather Ready Nation, Warn on Forecast, and emerging FACETs (Forecasting A Continuum of Environmental Threats (FACETs) STORM PREDICTION CENTER HAZARDOUS PHENOMENA • Thunderstorms • Hail, Wind, Tornadoes • Fire Weather • Mesoscale Winter Weather StormSPC Prediction Primary Products MissionCenter and Responsibility Convection-Allowing Model (CAM) Guidance at SPC • SPC forecasters have had access to CAM guidance since 2004 – Hazardous Weather Testbed Spring Forecasting Experiment evaluations – Year-round use in SPC operational severe weather forecasting – Primary partnerships with NCEP/EMC, NSSL, ESRL/GSD, OU/CAPS, NCAR, and AFWA • Typical CAM model characteristics – – – – Horizontal grid length ~3-4 km No parameterized convection Often “cold-start” from NAM or larger-scale model initial conditions Since 2007 pioneering work on real-time CAM ensemble systems • CAMs provide unique convective storm forecast guidance – Simulated reflectivity & synthetic satellite imagery – Extraction of storm characteristics using Hourly Max Fields (HMFs) • Updraft helicity, updraft/downdraft speed, 10-m wind, vertically integrated graupel Flashback – NPSR December 2012 Super Outbreak 27-28 April 2011 Images Valid 00z 28 April NAM 4 km Nest 24-hr forecast of 1 km AGL Simulated Reflectivity Observed Radar Base Reflectivity Mosaic Very few intense discrete storms predicted; model storms are too broad/weak and lack realism Observed radar displayed numerous discrete supercells and several embedded bow echoes Action: Started SPC-EMC bi-weekly telecons/webinars in Jan. 2013 Goal: Improve convective storm structure, mode and intensity Summary of Recent EMC Convection-Allowing Model Upgrades Characteristics HiResW NMMB HiResW ARW NAM Nest Implementation Date 11 June 2014 11 June 2014 12 August 2014 Horizontal Grid 3.6 km 4.2 km 4.0 km Vertical Levels 40 40 60 Initial Conditions RAP RAP NAM Microphysics Updated Ferrier WSM6 Ferrier-Aligo PBL/Turbulence MYJ MYJintensity so A key goal: Improve convective storm YSU structure, mode and simulated model storms are more similar to those observed by radar Radiation RRTM RRTM RRTM Conv. Param. None None None Domain CONUS CONUS CONUS Forecast Length 48 hrs 48 hrs 60 hrs Run Times 00, 12z 00, 12z 00, 06,12,18z Simulated Composite Reflectivity 22-hr Forecasts Valid 22z 20 May 2013 Vertical Cross-Section (top); Plan View (bottom) Experiments with New Ferrier-Aligo Microphysics => More intense, realistic storms April 27, 2014 • High Risk Over Parts of AR – Significant Tornadoes in AR and MS including one EF-4 tornado – 19 Fatalities including 16 in Mayflower-Vilonia AR (41 mile path length) • Deadliest Single Tornado in AR Since May 15, 1968 Destroyed Homes in Mayflower, AR NAM Nest Comparison 24-hr Forecast Valid 00z 28 April 2014 NAM Nest Parallel Observed Radar NAM Nest Operational • Parallel NAM Nest shows more intense, smaller-scale storm details • Most intense storms correctly predicted over central AR by parallel, whereas operational run has broader region of strong storms HiResW NMMB Comparison 24-hr Forecast Valid 00z 28 April 2014 HiResW NMMB Parallel Observed Radar HiResW WRF-NMM Operational • Neither HiResW NMMB nor WRFNMM highlighted central AR region • Both have limited storm coverage • NMMB parallel focuses too far west • WRF-NMM operational too far east HiResW ARW Comparison 24-hr Forecast Valid 00z 28 April 2014 HiResW ARW Parallel Observed Radar HiResW ARW Operational • Parallel HiResW ARW has more intense storms, especially over eastern AR (but too far east) • Parallel considered an improvement over operational, which focused weaker storms over MO April 28, 2014 • High Risk Over Parts of MS and AL – Significant Tornadoes in MS, AL and TN including EF-4 with 34 mile path length – 15 Fatalities (10 in MS) Also Hail to Baseball Size Tornado Near Louisville, MS NAM Nest Comparison 22-hr Forecast Valid 22z 28 April 2014 NAM Nest Parallel Observed Radar NAM Nest Operational • Parallel NAM Nest shows more intense storms and is more similar to observed radar • Both runs predict NE-SW oriented band of storms HiResW NMMB Comparison 22-hr Forecast Valid 22z 28 April 2014 HiResW NMMB Parallel Observed Radar HiResW WRF-NMM Operational • Neither run predicts primary linear mode • Parallel HiResW NMMB has improved storm details and is better indicating threat over northern MS, but is too slow with eastward progression HiResW ARW Comparison 22-hr Forecast Valid 22z 28 April 2014 HiResW ARW Parallel Observed Radar HiResW ARW Operational • Both runs indicate linear structure displaced to the southeast • HiResW ARW parallel appears to develop too strong a cold pool evidenced by bowing structure • Storms are more intense in parallel May 8, 2014 • Moderate Risk Parts of MN and IA – Wind Damage, Significant Hail, and Weak Tornadoes – Case Occurred During HWT Spring Forecasting Experiment House Damage in Red Wing, MN NAM Nest Comparison 20-hr Forecast Valid 20z 8 May 2014 NAM Nest Parallel Observed Radar NAM Nest Operational • Parallel NAM Nest shows more intense, smaller-scale storm details • Improved over Iowa with weaker reflectivity • Both runs predict spurious storms over eastern SD and northern WI HiResW NMMB Comparison 20-hr Forecast Valid 20z 8 May 2014 HiResW NMMB Parallel Observed Radar HiResW WRF-NMM Operational • Parallel HiResW ARW was much better over MN than operational run • RAP initial conditions may have contributed to improved performance HiResW ARW Comparison 20-hr Forecast Valid 20z 8 May 2014 HiResW ARW Parallel Observed Radar HiResW ARW Operational • Parallel HiResW ARW was much better over MN than operational run • RAP initial conditions may have contributed to improved performance June 3, 2014 • Major Severe Weather Event Over Central Plains and Lower MO Valley – Series of Severe Storms Caused Tornadoes and Significant Hail/Wind – Substantial Flooding parts of NE and IA including Omaha Metro Hail to Softball Size and Winds to 90 mph Baseball Hail in Norfolk, NE NAM Nest Comparison 24-hr Forecast Valid 00z 4 June 2014 NAM Nest Parallel Observed Radar NAM Nest Operational • Parallel NAM Nest shows more intense, smaller-scale storm details, but is worse with storm coverage and NW-SE axis of observed severe storms HiResW NMMB Comparison 24-hr Forecast Valid 00z 4 June 2014 HiResW NMMB Parallel Observed Radar HiResW WRF-NMM Operational • Parallel HiResW NMMB shows smaller-scale storms, but similar location and coverage • Neither run captures the NW-SE axis of severe storms HiResW ARW Comparison 24-hr Forecast Valid 00z 4 June 2014 HiResW ARW Parallel Observed Radar HiResW ARW Operational • Parallel HiResW ARW is much improved with intensity, location, and coverage of storms within the severe storm axis June 6, 2014 • Severe Weather Event Over Central & Southern High Plains – Bowing Squall Lines Moved Eastward Producing Tornadoes and Significant Hail & Wind in CO, NM, NE, KS, and TX – Last Day of HWT Spring Forecasting Experiment Hail to Baseball Size and Winds to 85 mph Storm near Scott City, KS NAM Nest Comparison 27-hr Forecast Valid 03z 7 June 2014 NAM Nest Parallel Observed Radar NAM Nest Operational • Parallel NAM Nest shows smallerscale storm details • Parallel and operational runs show similar placement and coverage of predicted storms, with north-south extent too limited HiResW NMMB Comparison 27-hr Forecast Valid 03z 7 June 2014 HiResW NMMB Parallel Observed Radar HiResW WRF-NMM Operational • Parallel HiResW NMMB has more limited storm coverage • Operational run provided better overall guidance despite displacement error to the west HiResW ARW Comparison 27-hr Forecast Valid 03z 7 June 2014 HiResW ARW Parallel Observed Radar HiResW ARW Operational • Similarly, parallel HiResW ARW storm coverage was more limited in north-south extent • Operational run provided better overall guidance Subjective Comparison of Operational and Parallel Runs During HWT Spring Forecasting Experiment NAM Nest HiResW ARW Parallel Better Parallel Better HiResW NMMB Focusing on reflectivity and UH forecasts for severe weather guidance, parallel runs subjectively rated as good as or better than the operational model: HiResW ARW – 18 out of 23 days HiResW NMMB – 21 out of 23 days NAM Nest – 17 out of 23 days June 16, 2014 • Significant Severe Weather Event Over Midwest • At least four EF-4 Tornadoes in Northeast Nebraska – Only 2 Fatalities in Sparsely Populated Area Despite Direct Hit of Pilger, NE Hail to Softball Size and Winds to 95 mph Twin Tornadoes in Pilger, NE NAM Nest and HiResW 21-hr Forecast Valid 21z 16 June 2014 NAM Nest HiResW NMMB Observed Radar HiResW ARW Pilger Storm NAM Nest and HiResW 24-hr Forecast Valid 00z 17 June 2014 NAM Nest HiResW NMMB • NAM Nest Performed Well with Primary Severe Storm Complex But Missed Pilger, NE Storm • HiResW Runs Performed Poorly and Did Not Predict Observed Convective Storm Evolution Observed Radar HiResW ARW June 30, 2014 • Significant Severe Weather Event Over Midwest • Two Derecho-Producing MCSs Tracked Along Similar Paths – Systems Moved at 50-60 kt Forward Speed – Widespread Wind Damage and Several EF-1 Tornadoes Hail to Baseball Size and Winds to 90 mph Lightning Time Lapse Over Chicago June 30, 2014 System 1 Chicago was hit by two derecho systems over a 4-hour period. The first struck around 00z and the second between 03-04z. We’ll look at the 24- and 27-hr forecasts valid at 00z and 03z. System 2 NAM Nest and HiResW 24-hr Forecast Valid 00z 1 July 2014 NAM Nest HiResW NMMB • Models did not capture well Derecho 1 although NAM Nest did show a QLCS across WI • NAM Nest correctly indicated a second QLCS across eastern IA; HiResW runs were slow developing 2nd system Observed Radar HiResW ARW Derecho 1 Derecho 2 NAM Nest and HiResW 27-hr Forecast Valid 03z 1 July 2014 NAM Nest HiResW NMMB • NAM Nest was quite good predicting second QLCS • HiResW runs “caught up” to some extent but were slow with northern part of system Observed Radar HiResW ARW HiResW & NAM Nest Objective Verification Performance Diagram – Reflectivity • Neighborhood verification (ROI=40 km) of reflectivity (13 Aug 2014 – 22 Nov 2014) o Period after new NAM implementation o Objective verification of reflectivity forecasts using a spatial neighborhood method o Performance of NAM Nest and HiResW runs is similar • HiResW ARW has slightly higher POD/CSI and lower FAR for 30 & 40 dBZ thresholds • Bias ~1 for all models o Indicates forecasts are equally plausible in statistical sense • Useful for CAM ensemble construction (SSEO) Higher POD Lower FAR Summary: NAM Nest & HiResW • New HiResW and NAM Nest models can provide better severe storm guidance compared to previous versions – Improved storm structure, mode, and intensity – HiResW - Full CONUS domain at 00 and 12z – HiResW - Use of RAP initial conditions enhances diversity in CAM suite HiResW - Increased horizontal/vertical resolution – NAM Nest and HiResW – Updated microphysics, diffusion, radiation • But, considerable challenges remain in convective-scale prediction for high-impact weather – Convective storm prediction is very hard to do well (where, when, etc.) – Foundational for Warn on Forecast, FACETs & Weather Ready Nation – Challenges include: Observational data, DA, model dynamic core and physics, information extraction, post-processing, and display, etc. Use of HRRR Model Guidance at SPC • SPC forecasters have had access to ESRL HRRR grids since April 2010 – Also evaluated in HWT Spring Forecasting Experiments – No surprise – HRRR is useful for short-term forecast applications • The NCEP version of the HRRR has a higher reflectivity bias than the ESRL version, but the timeliness and reliability is much improved for the NCEP HRRR • Concept of HRRR run-to-run continuity leading to higher forecaster confidence must be used with caution ̶ Implied spread-skill relationship is better in strongly forced situations • Issues with mixing in the warm-sector PBL lead to conditions that are too warm/dry and occasionally spurious convective initiation HRRR – September 20, 2014 Strongly Forced Case in Upper Midwest Consistent Model Forecasts Over Many Cycles Low-Topped Band of Storms in Cool, Low Dew Point Environment Mainly Wind Damage in Minnesota Storm Clouds Near Crookston, MN HRRR Run-to-Run Continuity Strongly Forced Case (“Comma Shape”) Images Valid 21z 20 September 2014 Observed Radar Forecast 12z Cycle: 9-hr HRRR Forecast HRRR Run-to-Run Continuity Strongly Forced Case (“Comma Shape”) Images Valid 21z 20 September 2014 Observed Radar Forecast 13z Cycle: 8-hr HRRR Forecast HRRR Run-to-Run Continuity Strongly Forced Case (“Comma Shape”) Images Valid 21z 20 September 2014 Observed Radar Forecast 14z Cycle: 7-hr HRRR Forecast HRRR Run-to-Run Continuity Strongly Forced Case (“Comma Shape”) Images Valid 21z 20 September 2014 Observed Radar Forecast 15z Cycle: 6-hr HRRR Forecast HRRR Run-to-Run Continuity Strongly Forced Case (“Comma Shape”) Images Valid 21z 20 September 2014 Observed Radar Forecast 16z Cycle: 5-hr HRRR Forecast HRRR Run-to-Run Continuity Strongly Forced Case (“Comma Shape”) Images Valid 21z 20 September 2014 Observed Radar Forecast 17z Cycle: 4-hr HRRR Forecast HRRR Run-to-Run Continuity Strongly Forced Case (“Comma Shape”) Images Valid 21z 20 September 2014 Observed Radar Forecast 18z Cycle: 3-hr HRRR Forecast HRRR Run-to-Run Continuity Strongly Forced Case (“Comma Shape”) Images Valid 21z 20 September 2014 Observed Radar Forecast 19z Cycle: 2-hr HRRR Forecast HRRR Run-to-Run Continuity Strongly Forced Case (“Comma Shape”) Images Valid 21z 20 September 2014 Observed Radar 20z Cycle: 1-hr HRRR Forecast Forecast In strongly forced situations, can have more confidence in consistent solutions HRRR Predicts Spurious Evening Convection over Kansas Five Consecutive Hourly ESRL HRRR Forecasts Initialized 18-22z Valid 23-06z on 17-18 September 2014 HRRR Forecasts valid 23z 17 Sep 2014 Consecutive Model Runs from 18z, 19z, 20z, 21z and 22z OBSERVED RADAR HRRR Forecasts valid 00z 18 Sep 2014 Consecutive Model Runs from 18z, 19z, 20z, 21z and 22z OBSERVED RADAR HRRR Forecasts valid 01z 18 Sep 2014 Consecutive Model Runs from 18z, 19z, 20z, 21z and 22z OBSERVED RADAR HRRR Forecasts valid 02z 18 Sep 2014 Consecutive Model Runs from 18z, 19z, 20z, 21z and 22z OBSERVED RADAR HRRR Forecasts valid 03z 18 Sep 2014 Consecutive Model Runs from 18z, 19z, 20z, 21z and 22z OBSERVED RADAR HRRR Forecasts valid 04z 18 Sep 2014 Consecutive Model Runs from 18z, 19z, 20z, 21z and 22z OBSERVED RADAR HRRR Forecasts valid 05z 18 Sep 2014 Consecutive Model Runs from 18z, 19z, 20z, 21z and 22z OBSERVED RADAR HRRR Forecasts valid 06z 18 Sep 2014 Consecutive Model Runs from 18z, 19z, 20z, 21z and 22z Summary: HRRR runs consistently predict spurious MCS rather than the elevated convective band to the northeast OBSERVED RADAR Summary: HRRR Run-to-Run Consistency and Forecaster Confidence • At times, especially during more strong forced situations, runto-run continuity can add to forecaster confidence in the utility of the HRRR forecasts • However, there are other times when the HRRR appears to “lock in” to a solution that turns out to be erroneous • The “spread/skill” relationship of time-lagged HRRR forecasts for deep convection can vary substantially • Forecasters should be judicious when applying traditional concepts of run-to-run continuity as a measure of confidence in the forecast accuracy The New Frontier: Convection-Allowing Ensembles • Lower predictability exists at the convective storm scale – Poor sampling of mesoscale environment (IC uncertainty) – Model physics errors tend to increase at smaller scales • A number of experimental convection-allowing ensemble systems have been developed in recent years – Information about range of convective storm possibilities – Probabilistic information on likelihood of convective storm occurrence, coverage, intensity, and proxy severe storm attributes • CAM ensembles are essential to support Weather Ready Nation high-impact weather needs 2014 Spring Forecasting Experiment Four Convection-Allowing Ensembles • OU/CAPS Storm-Scale Ensemble Forecast (SSEF) System ̶ ̶ Since 2007; 60-hr forecasts from 00z; 12z runs began in 2013 Primarily WRF-ARW; 4-km grid spacing; forecasts to 60hrs in 2014 Multi-physics, multi-initial conditions: applies SREF perturbations to NAM ICs Advanced physics, 3DVAR & radar data assimilation; available for HWT/SFE ̶ ̶ • SPC Storm-Scale Ensemble of Opportunity (SSEO) ̶ ̶ Since 2011; 36-hr forecasts at 00z & 12z; 7 members (2 time-lagged) Multi-model (ARW, WRF-NMM & NMM-B), multi-physics; ~4-km grid spacing Uses available deterministic models at SPC to process as an ensemble Basic data assimilation through NDAS; available year-round in SPC ̶ ̶ • Air Force Weather Agency (AFWA) Ensemble ̶ ̶ Since 2012; 60-hr forecasts at 00z & 12z; 10 members; 4-km grid spacing Single model (WRF-ARW), multi-physics, multi-initial conditions Cold start from downscaled global model forecasts (GFS, UM, CMC) No data assimilation; available year-round in SPC ̶ ̶ • National Severe Storms Laboratory (NSSL) WRF Ensemble ̶ ̶ ̶ First year; 36-hr forecasts at 00Z; 9 members; 4-km grid spacing Single model (WRF-ARW), single-physics, multi-initial conditions Cold start from 3-h forecasts of selected SREF members; year-round in SPC 2014 HWT CAM Ensemble UH Forecasts Max; Nprob>25;Nprob>100; Valid 21-00z 3 June 2014 CAPS SSEF NSSL Ens. SPC SSEO AFWA Ens. Max From Any Member NProb UH>25 m2/s2 NProb UH>100 m2/s2 Despite differences in CAM ensemble configurations and degree of complexity in data assimilation, IC/LBC perturbations, model and physics diversity, etc., overall performance was often similar on many days HWT CAM Ensemble Subjective Evaluation Hourly Probability of Reflectivity > 40 dBZ by Weighted Average • Overall scores very similar when applying weighted average across the ratings • Continues to suggest that CAM ensemble performance is similar regardless of system configuration and degree of complexity More Research Efforts on CAM Ensembles (But wait, there’s more) • NCAR has been developing an EnKF-based Mesoscale/CAM Ensemble System since 2011 – Considerably improved by 2013 for MPEX forecasting support • Goal for 2015: CONUS 10 member, 3 km ARW Ensemble with forecasts to 48 hrs and run daily in real-time for at least 1 year – Initialized by downscaling 10 analysis members of a continuously cycling EnKF 15 km mesoscale system comprised of 50 members – Blending of ensemble DA and prediction model can result in more dynamically consistent initialization and forecast process • NCAR Ensemble expected to part of HWT Spring Experiment and available for assessment in SPC operations (pending approval of HPC request) • This will be CAM ensemble #5 - How many ensembles are too many? – Help! Organized community-wide collaboration is clearly needed More Research Efforts on CAM Ensembles (But wait, there’s more) • For CAM ensembles, we are approaching where we were 5-10 years ago with deterministic CAMs – To enhance R2O/O2R process, considerable collaboration across the research and operational communities is needed to identify approaches feasible for operational implementation of CAM ensemble(s) – HWT is positioned to play a key role in the assessment process – Many key issues remain - will require sophisticated verification methods • • • • • • Multi-model versus single model Necessary horizontal and vertical resolution Scale-appropriate sources and perturbation strategies for ICs/LBCs Physics diversity and level of complexity Innovative statistical approaches to extract storm-scale information Creation of reliable probabilistic information for high-impact weather – Operational computing resources will ultimately inform CAM ensemble decision process More Research Efforts on CAM Ensembles (Provocative Slide to Spur Discussion) • Effective WCOSS utilization is a key foundational component • UCACN Recommendation – Simplify operational model suite and reduce number of modeling systems – Emulate other international modeling centers that have developed a more unified modeling system – Example: As GFS and GEFS approach resolutions of NAM and SREF, are all four systems needed? • Consider creating a team composed of operational forecasters, EMC and research modelers, and stakeholders in government and private sector to discuss and help plan future modeling suite – “Think outside the box” but recognize we will always have resource limits Two More Slides HRRR Performance: Warm-Sector PBL Mixing • The HRRR (and RAP) have a tendency to overmix the PBL, resulting in a boundary layer that is too warm and dry relative to observations. • In this example from 18 June 2014, the HRRR 6-h forecast of surface T/Td valid at 00z was 97/63 while observations showed 89/74. • The boundary layer becomes too deep/well-mixed, which can result in spurious convective initiation. 18Z NCEP HRRR, F006 Valid 00Z 06-18-14 00Z OBS SOUNDING in purple HRRR Performance Issue: Warm-Sector PBL Mixing 6-h forecast Valid 00Z June 18 Radar 00Z June 18 • Overmixing in the warm sector for this case led to an area of spurious convection across western Iowa and eastern Nebraska (and it was worse in later runs). • The RAP/HRRR group at ESRL/GSD are working on solutions for this issue.